1. Field of the Invention
The present invention relates to power line communications, and more particularly, to a configuration of a data coupler for power line communications.
2. Description of the Related Art
Power line communications (PLC), also known as broadband over power line (BPL), is a technology that encompasses transmission of data at high frequencies through existing electric power lines, i.e., conductors used for carrying a power current. A data coupler for power line communications couples a data signal between a power line and a communication device such as a modem.
An example of such a data coupler is an inductive coupler that includes a set of cores, and a winding wound around a portion of the cores. The inductive coupler operates as a transformer, where the cores are situated on a power line such that the power line serves as a primary winding of the transformer, and the winding of the inductive coupler is a secondary winding of the transformer.
The cores are typically constructed with magnetic materials, such as ferrites, powdered metal, or nano-crystalline material. The cores are electrified by contact with the power line and require insulation from the secondary winding. Typically, insulation is provided between the cores and secondary winding by embedding both the cores and the secondary winding in electrically insulating material, such as epoxy. During a molding process, the electrically insulating material reaches an elevated temperature. As the electrically insulating material, in a liquid state, flows around the cores, it begins to cool and contract. The thermal coefficient of expansion of the electrically insulating material is typically much higher than that of the core, and consequently, stress cracking of the electrically insulating material may occur during a transition from liquid to solid state.
In field operation, stiffly held magnetic cores made of brittle material may crack due to vibration or thermal expansion. There is a need for an inductive coupler configured to avoid such cracking.